Attempts to reduce power consumption of devices have been made. For example, a storage unit that has been conventionally configured by a volatile memory is configured by a non-volatile memory and a power supply to the storage unit is controlled. Specifically, the power supply to the storage unit is stopped when a central processing unit (CPU) is in a power-saving mode. When the CPU enters a normal-power mode, the power supply to the storage unit is started. With this configuration, energy consumption is reduced, compared to the case in which the volatile memory is used for the storage unit.
However, in a system of using only one type of memory as the storage unit, a performance of the entire device might be deteriorated due to deteriorated performance of the used memory.